Using the Panchromatic band for water column correction to derive water depth and spectral bottom signature: Landsat 8 OLIP bandset used for this work Purple=1, Blue=2, Green=3, PAN=4, Red=5, NIR=6 and SWIR1=7 |
Using pan sharpened images in this study Pan sharpening using Rstudio Brovey method |
![]() Calibration Blue vs Green
| ![]() Calibration Coastal vs Green ![]() Calibration Blue vs PAN |
![]() CC BOA WCC B=Coastal G=Green R=Blue | |
![]() B average bottom brightness |
ZLand In order to test 4SM against spectral variations of the bottom substrate, I can enforce a depth over land to apply the water column attenuation from image calibration, then process these "artificial shallow" pixels to see how well/bad this depth is retrieved. |
Result of this exercise From very shallow to very deep, the algorithm yields a surprisingly good estimation of depth; there is hardly any increase in uncertainty as depth increases. |
Noise But, wait: this does not include the quantization noise (mmm...)! I tried including 8_bits quantization of the computation of "artificial" pixels: absolutely NO change either of av_Z4SM or std_Z4SM for Zland=20m. |
GSD=15 m, pan-sharpened. NO smoothing applied. Just the estimated depth is "noisy", as an expression of
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PAN solution I suppose that this good result is in part a marked benefit of using the PAN band. |
Add heterogeneous atmosphere/water This does not account for the effect of the natural variations of the water/atmosphere optical properties, which can be very nasty in their own right, and increase dramatically deeper than ~half of the shallow depth range. |